A SOLID-STATE NMR AND X-RAY CRYSTALLOGRAPHIC INVESTIGATION OF DYNAMICDISORDER IN SOLID TETRAHYDRONAPHTHALENE DERIVATIVES

The solid state disorder of two tetrahydronaphthalene derivatives. -me thyl-N-methoxy-5,6,7,8-tetrahydro-1-naphthamide and 5,6,7,8-tetrahydro -1-naphthoic acid, was studied by solid state NMR and single crystal X -ray diffraction. The X-ray crystal structure of -methyl-N-methoxy-5,6 ,7,8-tetrahydro-1-naphthamide was obtained at 123 K. It indicated the presence of two distinct molecular conformations. Solid state C-13 CP/ MAS NMR data using the dipolar dephasing technique revealed that the t wo conformations of the molecule are dynamically disordered, while sol id state H-2 NMR data, collected on a specifically deuterated analog, were used to determine the populations of each conformation as well as an apparent activation energy. Solid state NMR experiments were also used to show that 5,6,7,8-tetrahydro-1-naphthoic acid possesses the sa me type of dynamic disorder.